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Surface coating of CdS nanoparticles over the ZnO nanorods have been performed by using simple successive ionic layer adsorption and reaction at room temperature. Initially, the seed/compact ZnO layer have been deposited via SILAR (successive ionic layer adsorption and reaction) on to fluorine doped tin oxide coated glass (FTO) substrate followed by synthesis of ZnO nanorods by chemical bath deposition method. The synthesized nano heterostructure was characterized by X-ray diffraction (XRD), UV–Vis spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX) and high resolution-transmission electron microscopy (HR-TEM) techniques. The photovoltaic performance of the cell was recorded with a conversion efficiency of 0.123% under 100 mW/cm 2 simulated sunlight at AM 1.5G conditions.

Simple and inexpensive wet chemical route, namely successive ionic layer adsorption and reaction (SILAR) is demonstrated to coat the inorganic semiconducting Bi 2 S 3 nanoparticles (NPs) at room temperature on chemical bath deposited vertically aligned ZnO nanorods (NRs). The films were characterized by X-ray diffraction (XRD), UV–vis spectroscopy, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX), Raman spectroscopy and surface profiler in order to confirm the crystal structure, optical properties, surface morphology, elemental compositions and film thickness. Finally, the solar cell device was formed by using Bi 2 S 3 coated ZnO NRs as photoanode, liquid electrolyte as hole conducting media and platinum (Pt) as a back contact. The power conversion efficiency ( η ) of 0.025% under illumination of simulated sunlight (AM 1.5 G, 100 mW/cm 2 ) was observed.

Recent improvements in electronic and optoelectronic devices based on solution processable polymers have motivated development of scalable processing techniques like Ultrasonic Spray technique. Including potential for roll to roll fabrication, it has many other strengths. However, with spray coating it can be difficult to prepare films with a smooth surface. Here, we present model for Ultrasonic Spray deposition of thin films, which establish a clear correlation between process parameters and the film formation process, which ultimately decide the structural features of the thin films. Based on the time to cover the spray deposition area by the sprayed droplets and the time for droplet evaporation, a balance parameter has been defined. It provides a mean to determine suitable process parameters for uniform film formation by Ultrasonic Spray method. The model is further modified for the region of higher solution flow rates, where non-uniformity in droplet distribution is introduced. The predictions based on the model have been experimentally verified with thin films of poly(3,4-ethylene dioxythiophene) doped with polystyrene sulphonic acid (PEDOT:PSS). The method presented here can be used to predict proper deposition parameters for smooth film deposition by Ultrasonic Spray technique. Finally, the effect of film morphology on the sheet resistance of thin films of PEDOT:PSS is also presented.

Room temperature chemical bath deposition (CBD) method was employed to anchor CdSe quantum dots (QD׳s) on mesoporous TiO2, exclusively without using linkers. The sizes of CdSe QD׳s were tuned simply by varying the deposition time in CBD method and uniform coverage of CdSe QD׳s on mesoporous TiO2 was achieved. The chemical approach provided in the present investigation is free from the post annealing treatment after the growth of QD׳s; essential to lower down the process cost. The red shift in absorption maxima was observed with respect to deposition time in the UV–vis spectra which strongly supports the size quantization effect. Finally, the synthesized CdSe sensitized TiO2 has successfully demonstrated the potential ability as a quantum dot sensitizer for solar cell application when illuminated with 50 mW/cm2 intensity (air mass 1.5)., BRS is thankful to DAE-BRNS sanctioned major research (2010/37C/5/BRNS).

Hydrogenated amorphous silicon (a-Si:H) films were deposited using pure saline (SiH 4 ) without hydrogen dilution by the hot wire chemical vapor deposition (HW-CVD) technique. The electrical, optical and structural properties of these films are systematically studied as a function of filament temperature ( T fil ). The device quality a-Si:H films which were obtained at high deposition rate (3≤ r d ≤85 A/s) using filament temperature (1400≤ T fil ≤1900 °C) without hydrogen dilution show good structural, optical and electrical properties. However, the films deposited at higher filament temperature show an amorphous-to-microcrystalline transition. The FTIR spectroscopic analysis showed that a-Si:H films deposited at low filament temperature contain hydrogen mainly in mono-hydride (Si–H) configuration whereas films deposited at higher filament temperature have hydrogen in di-hydride (Si–H 2 ) or poly-hydride (SiH 2 ) n complexes. The low hydrogen content ( C H ) in the films indicates that the growth of a-Si:H films is mainly from the atomic species (Si and H) evaporated from the hot filament and hydrogen is incorporated in the film via gas phase reactions and substrate–gas interactions. The band gap, however, was found to be ∼1.71 eV or much higher. We suggest high band gap at low hydrogen content may be due to the presence of microvoids. Raman spectroscopic analysis showed the increase in structural disorder and Rayleigh scattering with increase in filament temperature.

Hydrogenated amorphous silicon germanium (a-SiGe:H) films were deposited using SiH4 and GeH4 mixture without H dilution by hot wire chemical vapor deposition (HW-CVD) technique. The electrical, optical and structural of these films are systematically studied as a function of substrate temperature (Tsub). The FTIR spectroscopic studies showed that a-SiGe:H films deposited at high Tsub contain H mainly the monohydride configuration whereas the films deposited at low Tsub has H in polyhydrides or (Si–H2)n complexes form. The low CH in a-SiGe:H films indicates that the growth of film is mainly from the atomic species evaporated from the hot filament and H gets incorporated in the film via gas phase reactions and substrate–gas interactions. Raman spectroscopic studies showed that the structural order of a-SiGe:H films improve with increase in Tsub. The T sub =300 ° C was found to be the optimized substrate temperature for the synthesis of device quality a-SiGe:H films.

The electrical, structural and optical properties of undoped and phosphorus doped μc-Si:H films prepared by a HW-CVD technique have been studied. The hydrogen (H 2 ) dilution of silane has been varied carefully to produce undoped μc-Si:H films. The amorphous-to-microcrystalline transition was observed for a hydrogen dilution ratio >0.75. The phosphorus doped μc-Si:H films were deposited by varying the phosphine (PH 3 ) gas flow rate. The structural properties of these films have been investigated by Raman spectroscopy, low angle X-ray diffraction spectroscopy and Fourier transform infrared vibrational spectroscopy. Electrical characterization has been carried out by dark conductivity and charge carrier activation energy measurements. The phosphorus doped μc-Si:H films showed that the addition of PH 3 to the source gases promotes the growth of crystallinity. The increase in crystallite size and crystalline volume fraction with the addition of PH 3 to the source gases indicates that it enhances the crystallization of the μc-Si:H film. Low angle XRD studies shows that the PH 3 doped μc-Si:H does not show any preferential orientation crystallites. For optimized deposition conditions PH 3 doped μc-Si:H films with high dark conductivity (0.4 S/cm), low activation energy (0.03 eV) and high band gap (1.82 eV) were obtained with a high deposition rate (13 A/s). However, for these optimized conditions, the hydrogen content was relatively large (8.3 at.%).

Obtaining thickness uniformity over a large substrate area seems to be a bottleneck as far as the industrial applications of the hot-wire CVD (Cat-CVD) process is concerned. In order to address the different issues in this respect, we have simulated the hot-wire CVD growth process and proposed a proper filament geometry for maximum thickness uniformity. The hot filament was assumed as a one-dimensional assembly of point sources. Five types of commonly used filament geometries were considered for their performance to identify the best filament geometry for maximum thickness uniformity. Here, the chamber pressure was assumed to be low enough so that the Knudsen number Kn>1. Based on our results, we propose a parallel filament geometry for maximum thickness uniformity over large substrate areas. By applying the model further to the parallel filament geometry, the relations between substrate–filament distance and minimum filament length, as well as the number of parallel filaments and the separation between them, which are necessary for the required thickness uniformity over the given substrate area, were determined. The validity of the model was checked using the ‘Matched-Pair t-test’. The effect of chamber pressure on thickness uniformity and growth rate, when it is sufficiently high to make the Knudsen number Kn

The properties of a-SiGe:H films prepared by the glow discharge plasma CVD method at various interelectrode separation were studied systematically. This study was done at two different rf power densities. It has been found that interelectrode separation plays an important role in determining film properties. It shows a more marked effect on photosensitivity at lower rf power density than at higher rf power density. Photosensitivity, in general, decreased, whereas growth rate increased with the increase in interelectrode separation. High photosensitivity (1.3×105) was obtained even at higher growth rate (245 A/min) just by controlling the interelectrode separation. Bandgap of the films was about 1.4 eV. Structural properties of the films were studied by positron life time spectroscopy (PLTS).

We here present a way of preparing the polymer: fullerene BHJ using dual feed method which can lead to formation of pure phases. In this report, we present results of our initial experiments in this direction. The effect of process parameters on the thickness and surface roughness of the active layer has been discussed. The structural and optical properties have been studied using the optical microscope, UV—visible spectroscopy and photoluminescence spectroscopy. Significant PL quenching indicates efficient charge separation in the BHJ formed using this technique. We have also compared the BHJ thin films prepared with this dual feed ultrasonic technique with the single feed spray method. The BHJ formed using this technique has been used as an active layer in OSC.